Originally Posted by cencal83406

it might help to think of the application of PB days with the “partial” in mind first.

if you fly a 1-day GS over an X-day and it blocks in before 14:30 (later of actual or scheduled), you would expect your X-day to “begin” from 9 hours and 30 minutes from that point and go 24 hours.

Assume a non-transoceanic rotation:

Block in 14:00. Add :30 for release. Add 9:00 hours free from duty.

Result 23:30 X day “begin” (on your current X day). You’ll then add 24 hours to this and your new X day will end at 23:30 one day later. You’ll see this reflected as a PR.

If your 4-day green slip (or reroute or IA) touches 4 X days but your final duty period releases prior to 15:00 you should expect to see PB PB PB PR.